1. Field of the Invention
The present invention relates to a mobile network for allowing a mobile terminal to communicate with another terminal via a destination network and an IP (Internet Protocol) packet transferring method.
2. Description of the Background Art
IP packet communication is extensively used for data communication using personal computers and other data processing units. For IP packet communication, a particular IP address is assigned to each terminal in accordance with a network to which the terminal is usually connected. Therefore, to allow a mobile terminal handed over to another network to hold communication via the network, it is necessary to reassign an IP address particular to the new network to the mobile terminal. However, the other terminals cannot identify the mobile terminal handed over and provided with the new IP address.
Some different schemes have heretofore been proposed to implement data communication on a mobile terminal without changing an IP address when the terminal is handed over to a different network. IETF (Internet Engineering Task Force), for example, has recommended in RFC (Request for Comments) 2002 a mobile IP technology for encapsulating IP packets and transferring the encapsulated IP packets to a destination, i.e., transferring a given IP packet by using another IP packet. For encapsulation, there are available IP in IP Encapsulation recommended in IETF RFC 2003, Minimal Encapsulation within IP recommended in RFC 2004, and Generic Routing Encapsulation recommended in RFC 1701. The IP in IP Encapsulation scheme transfers a given IP packet by inserting it in another IP packet.
A conventional mobile network includes a fixed terminal, a notebook size, personal computer, handy phone or similar mobile terminal, a home agent for managing an IP address assigned to the mobile terminal, and foreign agents each for managing communication held on the mobile terminal at a particular destination. The fixed terminal is a personal computer or similar data processing unit situated at a fixed station. The home agent stores a binding table listing information for the transfer of encapsulated IP packets to the foreign agents.
The conventional mobile network has some problems left unsolved, as follows. Assume that a fixed terminal sends a plurality of packets of different degrees of priority to a mobile terminal connected to any one of the foreign agents. Then, the home agent encapsulates an IP packet with a low degree of priority and an IP packet with a high degree of priority by the same processing and then sends them to the foreign agent in the same QoS (Quality of Service) class. This is because QoS information is not registered at the binding table of the home agent.
Further, the binding table lists only a single destination for each home address or IP address assigned to the mobile terminal, limiting the transfer of encapsulated IP packets to a single destination. Consequently, when the foreign network is a mobile communication network, the mobile terminal cannot receive IP packets from a plurality of foreign agents at the same time. This makes, e.g., soft hand-over impracticable.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 7-129488, 9-326805, 10-313336 and 11-68842 and Japanese Patent 2,960,349.